A polyarylene resin-based resin, in particular, a polyphenylene sulfide resin (hereinafter referred to as a “PPS resin”) is widely used in electric and electronic components, mechanical components, automobile components or the like since it is improved in heat resistance, chemicals resistance, fire retardancy, rigidity, dimensional stability or the like.
However, as compared with other engineering plastics such as a syndiotactic polystyrene resin (hereinafter referred to as a “SPS resin”), a nylon 66 resin (hereinafter referred to as a “PA66 resin”) and a liquid crystal polyester resin (hereinafter referred to as a “LCP resin”), a PPS resin has a drawback that it is poor in voltage resistance. Therefore, in some applications, use of a PPS resin under a high voltage is restricted.
In addition, in recent years, higher value addition, including a reduction in size, has been required for electric and electronic components. Under such circumstances, insulating materials have been required which can withstand the use under electric and temperature environments which are severer than those in the past. In particular, development of an insulating material which is improved in voltage resistance, electric insulating properties, heat resistance, heat conductivity and fluidity in a well-balanced manner has been required.
In response to this requirement, a PPS resin to which a filler having a high degree of insulating properties and/or heat conductivity is added has been proposed. For example, a resin composition using talc (Patent Documents 1 to 3), a resin composition using silica-coated aluminum nitride (Patent Document 4) and a resin composition using silica-coated magnesium oxide (Patent Document 5) have been disclosed.
However, although talc improves anti-track properties and arc resistance, it does not improve voltage resistance sufficiently. Silica-coated aluminum nitride and silica-coated magnesium oxide improve heat conductivity. However, they do not improve voltage resistance.
In addition, in order to sufficiently improve electric insulating properties and/or heat conductivity, a large amount of filler has to be added. Addition of such a large amount of filler encounters a problem that fluidity and toughness are significantly lowered. As a method for recovering toughness which has been once lowered, addition of an elastomer and/or a fibrous filler is widely known. However, this method is not effective for a resin containing a large amount of filler.
Therefore, on a practical level, these resin compositions are not improved in electric insulating properties, heat conductivity, fluidity and toughness in a well-balanced manner. In addition, since no attempt has been made to improve voltage resistance, these resin compositions are not sufficient in voltage resistance.
Patent Document 1: JP-A-S53-5252
Patent Document 2: JP-A-H05-21650
Patent Document 3: JP-A-2003-128915
Patent Document 4: JP-A-2005-146214
Patent Document 5: JP-A-2005-306955
The invention has been made in view of the above-mentioned circumstances, and the object thereof is to provide a resin composition which is improved in voltage resistance, electric insulating properties, heat resistance, heat conductivity, fluidity and toughness in a well-balanced manner.